SATELLINE-EASy / SATELLINE-EASy 869
User Guide, Version 3.0
83
Vertical polarised antennas (antenna elements are in vertical position) are often used in radio
systems. In a system between a base station and substations vertical polarisation is
recommended. The radio modem antenna cannot be mounted on the same level as the other
substation antennas in the same building. The best way to distinguish from the other antennas
situated in the neighbourhood is to mount the antennas as far as possible from each other on
the altitude level. The best result is generally obtained when all the antennas are in the same
mast. With an extra ground plane between the antennas more distinction can be obtained
between the antennas in the mast.
Horizontal polarisation can be used in data transmission between two points. With the
polarisation attenuation more distinction is obtained to vertical polarised systems. The influence
of the directional patterns of the antennas must, however, be taken into consideration. If a
distinction to another interfering antenna is wanted with the horizontal polarised antennas there
must be a good attenuation of the back lobe. In addition to this the interfering radiator should
be situated behind the antenna.
When a system does not demand the use of an omni-directional antenna it is recommended that
directional antennas are used e.g. two-element yagis in permanent external installations. Please
note that as antenna amplification increases the setting of the direction of the antenna requires
more attention.
Base stations in high places should be supplied with high-Q cavity filters. Please note that the
higher the base station antenna, the larger the coverage area and in turn that the risk of
interference is also increased.
SATEL recommends the use of a band-pass filter with a large Q in the antenna cable of the base
station.
